This invention relates to a viewfinder. More specifically, this invention relates to a view finder capable of varying a magnification in accordance with a movement of taking lens of camera for zooming.
A view finder, capable of varying a magnification in accordance with a movement of taking lens of camera for zooming, usually includes a finder optical system capable of varying magnification of a finder image and an interlocking mechanism for shifting a movable lens in the finder optical system along the optical axis. A real-image type lens system is usually used for the finder optical system, which usually includes two movable lenses. Some finder has a diopter moving mechanism where eyepiece side lens is movable so as to match an eyesight of the user, such as a near-sighted or a far-sighted, in order to make the finder image of a subject clearer.
Aforementioned movable lenses in the finder optical system for zooming or diopter movement require high accuracy positioning and alignment. Also immovable optical elements other than the movable lenses must be fixed in the finder with high accuracy positioning and alignment. However, positioning and alignment of those optical elements are not always accurate because respective elements are held by respective holding members supported by respective local structure of the finder housing, which cause low optical performance. Also a guide shaft for guiding a movable lens for zooming is different one from a guide shaft for guiding a movable lens for diopter movement, which causes increase of the number of parts and manufacturing costs.
An object of the invention is to provide a view finder with high accuracy and low cost holding means for holding optical elements constituting a view finder.
To establish the object, a view finder of this invention comprises an object lens system at least one lens of which is movable along an optical axis of the object lens system being guided by a first guide shaft and an eye-piece lens system at least one lens of which is movable along an optical axis of the eye-piece lens system being guided by a second guide shaft, wherein the first guide shaft and the second guide shaft are positioned in axial alignment. It is preferable to make the first guide shaft and the second guide shaft formed integrally. The diameters of the two parts can be the same.
Also the optical axis of the object lens system and the optical axis of the eyepiece lens system can be different from each other, and the object lens system can be capable of varying a magnification of a finder image by moving at least one lens of the object lens system and the eyepiece lens system may be capable of diopter movement by moving at lease one lens of the eyepiece lens system.
There are two types of finder in ways of fixing the guide shaft. A first type view finder comprises a lens movable along the optical axis being guided by a guide shaft which is fixed to a finder housing and an immovable optical element mounted to the guide shaft which constitutes a finder optical system of the view finder together with the movable lens. A second type view finder comprises a lens movable along the optical axis being guided by a guide shaft and an immovable optical element which constitutes a finder optical system of the view finder together with the movable lens, wherein the guide shaft is fixed to the immovable optical element